Heating and hot water supply device

ABSTRACT

In a heating and hot water supply device comprising a burning means, a first heat exchanger, a circulation passage for circulating a heating thermal medium, a circulation pump, a first bypass passage, a second heat exchanger for hot water supply, a hot water supply passage, a second bypass passage bypassing the second heat exchanger, and a control unit, a distribution means is provided at a first branching portion of the first bypass passage and is capable of adjusting its distribution ratio for heating, or hot water supply, or simultaneous heating/hot water supply, during heating operation, the hot water supply passage is closed by a flow rate adjustment means provided in the hot water supply passage.

TECHNICAL FIELD

The present invention relates to a heating and hot water supply devicethat performs heating operation (i.e. room heating etc.) by applyingheat produced by combustion to a heating thermal medium, and that alsoperforms supply of hot water by applying heat to cold water by heatexchange with the heating thermal medium, and in particular relates tosuch a heating and hot water supply device that is capable of performingheating operation and hot water supply operation simultaneously.

BACKGROUND ART

From the past, heating and hot water supply devices that are capable ofsimultaneously performing heating operation and hot water supplyoperation have been widely utilized. As for example disclosed in PatentDocument #1, this type of heating and hot water supply device isprovided with a main heat exchanger and a heating apparatus, and thereare also provided a circulation passage through which a heating thermalmedium is circulated by a circulation pump between the main heatexchanger and the heating apparatus, and a bypass passage that branchesoff from the circulation passage and bypasses the heating apparatus.

A heat exchanger for hot water supply is provided in this bypasspassage, and heat can be applied by the heating thermal medium to waterflowing along a hot water supply passage through the heat exchanger forhot water supply. A distribution flow rate adjustment means is providedat the portion where the circulation passage and the bypass passagebranch apart, so that it is possible to adjust the distribution ratiobetween the heating thermal medium that goes to the heating apparatusand the heating thermal medium that goes to the heat exchanger for hotwater supply.

During heating operation, fuel is combusted, and heat is applied to theheating thermal medium by the main heat exchanger, and the distributionflow rate adjustment means is adjusted so that the heating thermalmedium circulates entirely within the circulation passage. And, afterthe heating thermal medium to which heat has been applied dissipatesheat in the heating apparatus, it returns back to the main heatexchanger.

When hot water supply operation is to be performed, the distributionflow rate adjustment means is adjusted so that part or all of theheating thermal medium to which heat has been applied circulates in thebypass passage, and hot water is supplied by heat being applied to thewater flowing in the hot water supply passage by the heat exchanger forhot water supply that is provided in the bypass passage. Moreover, thereare also some systems in which, instead of a distribution valve beingprovided, hot water supply operation is performed by operating a threeway valve, so that all of the heating thermal medium circulates in thebypass passage.

A hot water supply bypass passage that bypasses the heat exchanger forhot water supply is provided to the hot water supply passage, and thehot water supply temperature is adjusted by mixing fresh water thatflows in the hot water supply bypass passage into the hot water that hasbeen heated by the heat exchanger for hot water supply. As for exampledisclosed in Patent Document #1, the flow rate of the cold water flowingin the hot water supply bypass passage may be regulated by providing abypass valve in the hot water supply bypass passage, and the hot watersupply temperature may be adjusted by mixing the cold water into thewater to which heat has been applied. Alternatively, a mixing valve maybe provided at the portion where the hot water supply passage and thehot water supply bypass passage join together, so that the mixing ratiobetween the water to which heat has been applied and the cold water canbe adjusted, and thereby the hot water supply temperature is adjusted bymixing together the water to which heat has been applied and the coldwater.

PRIOR ART DOCUMENT Patent Document

Patent Document #1: Japanese Laid Open Patent Publication 2005-337632.

SUMMARY OF INVENTION Technical Problem

When a heating and hot water supply device of this type performs heatingoperation, the heating thermal medium circulates at high temperaturebetween the heating apparatus and the main heat exchanger. However, thedistribution valve or three way valve that is provided at the branchingportion between the circulation passage and the bypass passage is notgenerally a distribution valve or a three way valve having a fullyclosing function which is usually high in price, so that, during heatingoperation, it is not possible perfectly to shut off outflow of theheating thermal medium to the bypass passage. Because of this, heat isapplied to the water within the heat exchanger for hot water supply bythe heating thermal medium at high temperature which flows out into thebypass passage due to heating operation.

Furthermore, even outside the heat exchanger for hot water supply, thetemperature of the water within the hot water supply passage is elevatedby hot water heat transfer. For example, with the heating and hot watersupply device of Patent Document #1, the temperature of the water in thehot water supply passage on the upstream side and on the downstream sidethan the heat exchanger for hot water supply, and also the temperatureof the water in the hot water supply bypass passage, are both elevatedby such heat transfer. When hot water supply is started in this state,there is a risk that perhaps the hot water provided will be hotter thanthe user anticipates, since the temperature of the water in the hotwater supply passage and the temperature of the water in the hot watersupply bypass passage are unduly high directly after the hot watersupply starts.

Moreover, one expedient for preventing this type of hot water output atunduly high temperature is for the distribution valve or the three wayvalve at the portion where the circulation passage and the bypasspassage branch apart to be provided as a distribution valve or a threeway valve having a fully closing function, so that the heating thermalmedium is positively prevented from flowing out, but this is not apreferred solution because it increases the manufacturing cost.

The object of the present invention is to provide a heating and hotwater supply device that is capable of avoiding output of hot water atexcessively high temperature even when hot water is being suppliedduring heating operation, without employing any distribution valve orthree way valve having a fully closing function.

Means to Solve the Problem

The present invention presents a heating and hot water supply device,comprising a combustion means, a main heat exchanger, a circulationpassage connected to the main heat exchanger and to a heating apparatus,a circulation pump provided in the circulation passage, a first bypasspassage that branches off from the circulation passage and bypasses theheating apparatus, a heat exchanger for hot water supply provided in thefirst bypass passage, and a hot water supply passage for supplying coldwater to the heat exchanger for hot water supply, and for supplying hotwater heated by the heat exchanger for hot water supply to apredetermined set hot water supply temperature wherein: a distributionmeans is provided at a first branching portion of the first bypasspassage, and a distribution ratio of the distribution means can beadjusted so that heating operation, or hot water supply operation, orsimultaneous heating operation and hot water supply operation becomepossible; and a second bypass passage that bypasses the heat exchangerfor hot water supply is provided in the hot water supply passage; a flowrate detection means provided on an upstream side than a second brachingportion of the second bypass passage; a flow rate adjustment means forthe hot water supply passage is provided at the second branching portionor on the downstream side than the second branching portion and also atthe upstream side than the heat exchanger for hot water supply; and,during heating operation, the hot water supply passage is closed by theflow rate adjustment means.

According to the constitution described above, since the hot watersupply passage is closed by the flow rate adjustment means duringheating operation, therefore heat transfer to the water is prevented bythe flow rate adjustment means. Accordingly, even if the temperature ofwater within the hot water supply passage is elevated by the heatingthermal medium that has flowed out from the distribution means duringheating operation via the heat exchanger for hot water supply, it isstill possible to suppress elevation of the temperature of the water onthe upstream side than the flow rate adjustment means. When hot water issupplied in this state, since the water whose temperature has beenprevented from rising is supplied as hot water through the second bypasspassage, accordingly it is possible to avoid supply of output hot waterat an excessively high temperature.

The flow rate adjustment means may be a distribution valve provided atthe second branching portion.

According to the constitution described above, during the heatingoperation, along with the hot water supply passage being closed by thedistribution valve, the second bypass passage is opened. Therefore, evenif during heating operation the temperature of the water in the hotwater supply passage is elevated by the heating thermal medium,transmission of heat is prevented by the distribution valve, and it ispossible to suppress elevation of the temperature of the water on theupstream side than the distribution valve. Moreover, when supply of hotwater is started in this state, since this water whose temperature hasbeen prevented from rising is supplied as hot water via the secondbypass passage, accordingly it is possible to avoid supply of output hotwater at an excessively high temperature.

The flow rate adjustment means may be a flow rate regulation valveprovided more downstream than the second branching portion and moreoveron the upstream side of the heat exchanger for hot water supply, and thebypass flow rate regulation valve may be provided in the second bypasspassage; and, during heating operation, the bypass flow rate regulationvalve may be opened.

According to the constitution described above, during the heatingoperation, the flow rate regulation valve closes the hot water supplypassage, and the second bypass passage is opened. Therefore, even ifduring heating operation the temperature of the water in the hot watersupply passage is elevated by the heating thermal medium, transmissionof heat is prevented by the flow rate regulation valve, and it ispossible to suppress elevation of the temperature of the water on theupstream side than the flow regulation valve. Moreover, when supply ofhot water is started in this state, since the water whose temperaturehas been prevented from rising is supplied as hot water via the secondbypass passage, accordingly it is possible to avoid supply of output hotwater at an excessively high temperature.

Advantages of Invention

According to the present invention, it is possible to provide a heatingand hot water supply device that is capable of avoiding output of hotwater at excessively high temperature when supplying hot water duringheating operation, without employing a high priced distribution valve orthree way valve having a fully closing function.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a figure schematically showing a heating and hot water supplydevice according to the present invention;

FIG. 2 is a graph showing the hot water supply temperature when a hotwater supply passage is closed during heating operation;

FIG. 3 is a graph showing the hot water supply temperature when a hotwater supply passage is not closed during heating operation according tothe prior art; and

FIG. 4 is a figure schematically showing a heating and hot water supplydevice according to a second embodiment.

DESCRIPTION OF EMBODIMENTS

In the following, implementations of the present invention will beexplained on the basis of embodiments.

First Embodiment

First, the overall constitution of the heating and hot water supplydevice 1 of the present invention will be explained with reference toFIG. 1.

The heating and hot water supply device 1 performs heating operation bycirculating a heating thermal medium, to which heat has been applied byheat exchange with combustion gases generated by a combustion unit 2, toa heating apparatus (not shown in the figures), and also performs hotwater supply operation by supplying cold water to which heat has beenapplied by heat exchange with the heating thermal medium, whileadjusting its temperature to a set hot water supply temperature.

The heating and hot water supply device 1 comprises a combustion unit 2which is a combustion means that mixes fuel gas and air together andcombusts them, a main heat exchanger 10 that applies heat to the heatingthermal medium by heat exchange with the combustion gases generated bythe above combustion, a circulation passage 4 that connects the mainheat exchanger 10 with the heating apparatus, a circulation pump 11 thatcirculates the heating thermal medium through the circulation passage 4,and so on.

Moreover, the heating and hot water supply device 1 further comprises afirst bypass passage 12 that branches off from the circulation passage 4and bypasses the heating apparatus, a heat exchanger for hot watersupply 20 that is provided in the first bypass passage 12, a hot watersupply passage 21 for supplying fresh water to the heat exchanger forhot water supply 20 and for supplying hot water to which heat has beenapplied by the heat exchanger for hot water supply 20, and so on. And afirst distribution valve 15 (a distribution means) is provided in thefirst branching portion where the first bypass passage 12 branches offfrom the circulation passage 4.

Furthermore, the heating and hot water supply device 1 comprises acontrol unit 7 that receives detection signals from temperature sensorsetc. and controls heating operation and hot water supply operation etc.by operating the various units described above, and also comprises a boxshaped casing 8 that receives the devices described above and so on.

Next, the combustion unit 2 will be explained.

The combustion unit 2 comprises an intake passage 40 that takes in airfor combustion, a fuel gas passage 41 that supplies fuel gas providedfrom the exterior into the intake passage 40, a combustion fan 24 thatblows the resulting mixture of air and fuel gas through the intakepassage 40, and a burner 43 that combusts the mixture gas that has beenblown in by the combustion fan 42.

The flow rate of the air for combustion is controlled by the rotationalspeed of the combustion fan 42. Moreover, a venturi mixer 44 is providedat the downstream end of the fuel gas passage 41, and controls the flowrate of the fuel gas supplied by the rotational speed of the combustionfan 42. An electromagnetic valve 45 is provided in the fuel gas passage41, and, by opening and closing the electromagnetic valve 45, the fuelgas supply is started or stopped.

The burner 43 starts combustion by igniting the mixture gas blown by thecombustion fan 42 with an ignition device 46 that is provided below theburner 43. Moreover, a combustion sensor 47 is provided below the burner43 and detects the state of combustion.

The main heat exchanger 10 is provided below the ignition device 46 andthe combustion sensor 47. This main heat exchanger 10 and the burner 43etc. are housed within a housing 48 that defines a passage for thecombustion gases. The combustion gases generated by combustion of themixture gas in the burner 43 are sent to the main heat exchanger 10,and, after having exchanged heat with the heating thermal medium, areexhausted to the exterior via an exhaust passage 49 that extends fromthe lower portion of the housing 48. An exhaust temperature sensor 50 isprovided at the downstream end portion of the exhaust passage 49, and iscapable of detecting the temperature of the exhausted combustion gases.

The main heat exchanger 10 comprises a primary heat exchanger 10 a thatrecovers sensible heat from the combustion gases, and a secondary heatexchanger 10 b that recovers latent heat from the combustion gases.These two heat exchangers 10 a,10 b are connected so that the heatingthermal medium to which heat has first been applied by the secondaryheat exchanger 10 b then receives further application of heat from theprimary heat exchanger 10 a. A drainage passage 51 is provided at thebottom portion of the housing 48, and discharges drainage water that hasbeen condensed in the secondary heat exchanger 10 b to the exterior. Inorder to prevent the combustion gases from flowing out, a drainage trap52 is provided at the downstream end portion of the drainage passage 51.

Next, the circulation passage 4 will be explained.

A first temperature sensor 13 which is capable of detecting thetemperature of the heating thermal medium flowing into the main heatexchanger 10 is provided in the circulation passage 4 between thecirculation pump 11 and the main heat exchanger 10. And a secondtemperature sensor 14 that is capable of detecting the temperature ofthe heating thermal medium to which heat has been applied by the mainheat exchanger 10 is provided on the downstream side of the main heatexchanger 10.

A first distribution valve 15 is provided at the first portion where thefirst bypass passage 12 branches off from the circulation passage 4, atthe downstream side of the main heat exchanger 10. The firstdistribution valve 15 is capable of performing distribution whileadjusting the distribution ratio of the heating thermal medium to whichheat has been applied by the main heat exchanger 10 between thecirculation passage 4 and the first bypass passage 12. The first bypasspassage 12 rejoins the circulation passage 4 at the upstream side of thecirculation pump 11.

A pressure relief valve 16 that relieves the pressure in the circulationpassage 4 is provided between the main heat exchanger 10 and the firstdistribution valve 15. And a heating return temperature sensor 17 thatis capable of detecting the temperature of the heating thermal mediumreturning from the heating apparatus is provided at the upstream side ofthe circulation pump 11. Moreover, a replenishment passage 18 forreplenishing the heating thermal medium is connected between thecirculation pump 11 and the heating return temperature sensor 17.

Next, the heat exchanger for hot water supply 20 will be explained. Theheat exchanger for hot water supply 20 provided in the first bypasspassage 12 is a plate type heat exchanger. In such a plate type heatexchanger, a plurality of heat exchange plates are laminated together sothat passages are defined between the heat exchange plates. Within theheat exchanger for hot water supply 20, the heating thermal medium andthe supply water for hot water flow through alternate passages definedbetween the heat exchange plates, arranged so that these flows opposeone another and do not mix with one another. The surface area of each ofthe heat exchange plates is formed with irregular roughnesses, in orderto enhance the heat exchange efficiency.

Next, the hot water supply passage 21 will be explained. The hot watersupply passage 21 is capable of supplying fresh water to the heatexchanger for hot water supply 20, and also is capable of supplying hotwater to which heat has been applied by the heat exchanger for hot watersupply 20 to a hot water supply faucet etc., and moreover a secondbypass passage 22 is provided that branches off from the hot watersupply passage 21 and bypasses the heat exchanger for hot water supply20. A second distribution valve 23, which is equivalent to a flow rateadjustment means, is provided at the second branching portion betweenthe hot water supply passage 21 and the second bypass passage 22. Thesecond distribution valve 23 is capable of fresh water distribution byadjusting the distribution ratio between the hot water supply passage 21and the second bypass passage 22. Due to this, the second distributionvalve 23 is capable of adjusting the flow rate of fresh water flowinginto the hot water supply passage 21.

A flow rate regulation valve 24, a hot water supply amount sensor 25,and an intake water temperature sensor 26 are provided at the upstreamside than the second distribution valve 23. The flow rate regulationvalve 24 is capable of regulating the flow rate of the fresh water thatpasses into the second distribution valve 23. The hot water supplyamount sensor 25 is capable of detecting the flow rate of the freshwater that has been thus regulated. And the intake water temperaturesensor 26 is capable of detecting the temperature of the fresh intakewater that passes into the second distribution valve 23.

An output hot water temperature sensor 27 is provided between thelocation where the hot water supply passage 21 and the second bypasspassage 22 join together and the heat exchanger for hot water supply 20.The output hot water temperature sensor 27 is capable of detecting thetemperature of the hot water outputted from the heat exchanger for hotwater supply 20. And a hot water supply temperature sensor 28 isprovided downstream of the location where the hot water supply passage21 and the second bypass passage 22 join together. The hot water supplytemperature sensor 28 is capable of detecting the temperature of themixture water that results from the mixing together of the hot water towhich heat has been applied by the heat exchanger for hot water supply20 and the fresh water flowing through the second bypass passage 22.

Next, the control unit 7 will be explained.

Although not shown in figures, the control unit 7 is capable ofreceiving detection signals from the various temperature sensors etc.provided within the heating and hot water supply device 1, and moreoveris connected to the circulation pump 11 and the first distribution valve15 etc. so as to be capable of controlling them. Moreover, the controlunit 7 is connected to an operation device (operation terminal) that isprovided within the building to which the heating and hot water supplydevice 1 is provided, so as to be capable of communicating therewith.The operation device may, for example, comprise a display unit that iscapable of displaying, for example, temperature and operating status andso on, and an operating unit for performing setting of the heatingtemperature and the hot water supply temperature, and for performingstarting actuation and stopping actuation for heating operation and soon.

Next, the operation and the advantageous effects of the heating and hotwater supply device 1 will be explained with reference to FIGS. 1through 3. When heating operation is started, the control unit 7 adjuststhe first distribution valve 15 so that the heating thermal mediumcirculates only in the circulation passage 4, and, along with operatingthe circulation pump 11 and causing the heating thermal medium tocirculate in the circulation passage 4, also operates the combustion fan42 and the ignition device 46 and combusts mixture gas with the burner43. The combustion gases that are generated apply heat to the heatingthermal medium in the main heat exchanger 10. And, during the heatingoperation, the control unit 7 adjusts the second distribution valve 23so that, along with the hot water supply passage 21 being closed, thesecond bypass passage 22 is opened. Due to the heating operation beingcontinued, the heating thermal medium comes to be circulated at apredetermined temperature.

FIG. 2 is a graph showing one example of the temperature detected by theoutput hot water temperature sensor 27 and the temperature detected bythe hot water supply temperature sensor 28 before and after hot watersupply operation starts during heating operation, as the opening amountof the second distribution valve 23 changes over the passage of time.The opening amount of the second distribution valve 23 is expressed by anumber of steps along the second vertical axis; for example, thecompletely closed state when the hot water supply passage 21 is closedis step 1700, while the state in which the distribution ratio betweenthe hot water supply passage 21 and the second bypass passage 22 is 2:3is step 1000. At this time, the temperature of the fresh water is 22° C.

During heating operation, a part of the heating thermal medium that iscirculating flows out from the first distribution valve 15 and flowsinto the first bypass passage 12. Heat is applied to the water in thehot water supply passage 21 by the heating thermal medium in the heatexchanger for hot water supply 20, and the temperature of the waterwithin the hot water supply passage 21 that is detected by the outputhot water temperature sensor 27 that is close to the heat exchanger forhot water supply 20 is raised to around 64° C., and the temperature ofthe water detected by the hot water supply temperature sensor 28 becomesaround 33° C. Although not shown in the figure, since the hot watersupply passage 21 is closed by the second distribution valve 23 so thattransfer of heat from the water that has been heated by the heatexchanger for hot water supply 20 to the water on the upstream side ofthe second distribution valve 23 is prevented, accordingly thetemperature more upstream than the second distribution valve 23 is low.

Supply of hot water is started near the elapsed time of 3 seconds inFIG. 2; that is, hot water supply operation is started when, due to ahot water supply faucet etc. being opened, the hot water supply amountsensor 25 detects a flow rate greater than or equal to the predeterminedflow rate. The control unit 7 adjusts the first distribution valve 15 sothat the heating thermal medium circulates only in the first bypasspassage 12, and thereby heat is applied by the heating thermal medium tothe water in the heat exchanger for hot water supply 20. Since, evenafter the hot water supply operation has started, the hot water supplypassage 21 remains closed for one second, for example, rising oftemperature at the upstream side than the second distribution valve 23is suppressed and hot water is supplied via the second bypass passage22. Accordingly, although the water at the upstream side of the hotwater supply temperature sensor 28 whose temperature has been raised issupplied as hot water whose temperature has been elevated by about +4°C., since the amount of this elevation is small and water is immediatelysupplied as hot water via the second bypass passage 22, accordingly itis possible to avoid supply of hot water at an excessively hightemperature.

Next, after for example one second has elapsed from the start of hotwater supply, the control unit 7 gradually adjusts the opening amount ofthe second distribution valve 23, for example from 1700 steps to 1000steps in three seconds, so that fresh water gradually flows into the hotwater supply passage 21. Since the water at high temperature in the heatexchanger for hot water supply 20 is gradually outputted as hot water,accordingly the output hot water temperature is elevated. However, theamount of elevation of the hot water supply temperature is low, becausethis output hot water at high temperature and the cold water at lowtemperature are mixed together.

Since, in this manner, the water in the hot water supply passage 21whose temperature has been elevated during the heating operation issupplied as hot water while being mixed a little at a time with freshwater passing through the second bypass passage 22, accordingly it ispossible to avoid the output of hot water at an excessively hightemperature due to the water in the hot water supply passage 21 whosetemperature has been elevated during the heating operation. Moreoverwhen, on the basis of the set hot water supply temperature and theoutput hot water temperature detected by the output hot watertemperature sensor 27 etc., the control unit 7 determines thatsimultaneous heating operation and hot water supply operation arepossible, then the control unit 7 adjusts the distribution ratio of thefirst distribution valve 15 and performs simultaneous heating operationand hot water supply operation.

FIG. 3 is a graph showing one example of change over the passage of timeof the output hot water temperature and the hot water supplytemperature, when, in order to recreate the operation of a prior artheating and hot water supply device, the second distribution valve 23 isfixed at 1000 steps, and the hot water supply passage 21 is not closedduring space heating operation. The temperature of the fresh water atthis time is 24° C.

Since the hot water supply passage 21 is not closed during the spaceheating operation, accordingly the temperature of the water in the heatexchanger for hot water supply 20 is elevated by the heating thermalmedium and convection takes place, and water at high temperature flowsin the hot water supply passage 21 and in the second bypass passage 22.Due to this, heat is transmitted to the upstream side and the downstreamside of the heat exchanger for hot water supply 20, and the water in thehot water supply passage 21 and in the second bypass passage is heatedup to a high temperature. The temperature of the water more downstreamthan the portion where the hot water supply passage 21 and the secondbypass passage 22 come together is also elevated due to the water athigh temperature, and the temperature detected by the hot water supplytemperature sensor 28 goes up to around 49° C., which is a highertemperature than in the case of FIG. 2. Although not shown in thefigure, in a similar manner, heat is also transmitted to the water atthe upstream side of the second distribution valve 23, which accordinglyalso goes to high temperature.

When in FIG. 3 the hot water supply is started at around 3 secondselapsed time, since the second distribution valve 23 is not closing thehot water supply passage 21, accordingly the fresh water that is takenin by the second distribution valve 23 as intake water is distributed tothe hot water supply passage 21 and to the second bypass passage 22.Therefore, the water at high temperature in the heat exchanger for hotwater supply 20 is outputted, and the output hot water temperaturerises. And, when at around 6 seconds elapsed time this water at hightemperature passes down the second bypass passage 22 and mixes with thewater whose temperature has been raised and is supplied as hot water,the hot water supply temperature is elevated. Since the temperature ofthe water that is mixed in through the second bypass passage 22 is high,accordingly the magnitude of this elevation is around +14° C., which islarge as compared with the case of FIG. 2. Accordingly, in the case ofFIG. 3, the hot water continues to be supplied at a high temperature fora considerable while after the start of hot water supply, and there is adanger of output of hot water at an excessively high temperature, sincethe hot water supply temperature rises greatly partway through thissupply.

As explained above, with the heating and hot water supply device 1 ofthe present invention, due to the fact that the hot water supply passage21 is closed by the second distribution valve 23 during the spaceheating operation, it is possible to suppress elevation of thetemperature of the water in the hot water supply passage 21, so that itis possible to avoid outputting of excessively hot water. Moreover,since the water within the hot water supply passage 21 whose temperaturehas become elevated during heating operation is gradually mixed withfresh water supplied via the second bypass passage 22 and is thensupplied as hot water, accordingly it is possible to avoid anyoutputting of excessively hot water.

Second Embodiment

Next, a heating and hot water supply device 1A according to a secondembodiment will be explained with reference to FIG. 4.

In the heating and hot water supply device 1A, instead of the seconddistribution valve 23 of the first embodiment which is an adjustmentmeans for adjusting the flow rate in the hot water supply passage 21, itis possible to adjust the hot water supply flow rate with a flow rateregulation valve 23A provided in a hot water supply passage 21A and witha bypass flow rate regulation valve 24A provided in a second bypasspassage 22A. The second bypass passage 22A branches off from between aflow rate adjustment valve 23A and a hot water supply amount sensor 25A.

Next, the operation and the advantageous effects of the heating and hotwater supply device 1A will be explained.

During heating operation, the control unit 7A closes the flow rateadjustment valve 23A and opens the bypass flow rate regulation valve 24Aso that the hot water supply passage 21A is closed and the second bypasspassage 22A is opened. Even if the temperature of the water in the hotwater supply passage 21A becomes elevated during the heating operationby the heating thermal medium, rise of the temperature of the freshwater at the upstream side than the flow rate adjustment valve 23A issuppressed, since the flow rate adjustment valve 23A is closed.

When in this state hot water supply operation is started, since freshwater rising of whose temperature has been suppressed is supplied viathe second bypass passage 22A, accordingly it is possible to avoidoutput of hot water at an excessively high temperature when hot watersupply starts. Moreover, the control unit 7A adjusts the flow rateadjustment valve 23A so that a lot of fresh water flows into the hotwater supply passage 21 gradually. Since in this manner, during spaceheating operation, the water in the hot water supply passage 21A whosetemperature has been elevated is mixed with fresh water a little bit ata time for supply of hot water, accordingly it is possible to avoid theoutput of hot water at an excessively high temperature due to the hotwater in the hot water supply passage 21A. Moreover when, on the basisof the set hot water supply temperature and the output hot watertemperature detected by the output hot water temperature sensor 27A andso on, the control unit 7A is able to determine that simultaneousheating operation and hot water supply operation are possible, then thecontrol unit adjusts the distribution ratio of the first distributionvalve 15A and performs simultaneous space heating operation and hotwater supply operation.

Apart from the above, for a person skilled in the art, it would bepossible to implement the present invention by adding various changes tothe embodiments described above without deviating from the gist of theinvention, and the present invention is to be understood as includingsuch variant embodiments.

DESCRIPTION OF REFERENCE NUMERALS

-   1: heating and hot water supply device-   2: combustion unit (combustion means)-   4: circulation passage-   7: control unit-   8: case-   8 a: bottom plate-   10: main heat exchanger-   11: circulation pump-   12: first bypass passage-   15: first distribution valve (distribution means)-   20,20A: heat exchanger for hot water supply-   21,21A: hot water supply passage-   22,22A: second bypass passage-   23: second distribution valve (flow rate adjustment means)-   23A: flow rate adjustment valve-   24,24A: flow rate regulation valve-   25,25A: hot water supply amount sensor-   27: output hot water temperature sensor-   28: hot water supply temperature sensor

1. A heating and hot water supply device, comprising a combustion means,a main heat exchanger, a circulation passage connected to the main heatexchanger and to a heating apparatus, a circulation pump provided in thecirculation passage, a first bypass passage that branches off from thecirculation passage and bypasses the heating apparatus, a heat exchangerfor hot water supply provided in the first bypass passage, and a hotwater supply passage for supplying cold water to the heat exchanger forhot water supply, and for supplying hot water heated by the heatexchanger for hot water supply to a predetermined set hot water supplytemperature, wherein: a distribution means is provided at a firstbranching portion of the first bypass passage, and a distribution ratioof the distribution means can be adjusted so that heating operation, orhot water supply operation, or simultaneous heating operation and hotwater supply operation, become possible; and a second bypass passagethat bypasses the heat exchanger for hot water supply is provided in thehot water supply passage; a flow rate detection means is provided on anupstream side than a second branching portion of the second bypasspassage; a flow rate adjustment means for the hot water supply passageis provided at the second branching portion or on the downstream sidethan the second branching portion and also at an upstream side than theheat exchanger for hot water supply; and, during heating operation, thehot water supply passage is closed by the flow rate adjustment means. 2.The heating and hot water supply device according to claim 1, whereinthe flow rate adjustment means is a distribution valve provided at thesecond branching portion.
 3. The heating and hot water supply deviceaccording to claim 1, wherein the flow rate adjustment means is a flowrate regulation valve provided more downstream than the second branchingportion and moreover on the upstream side than the heat exchanger forhot water supply, and the bypass flow rate regulation valve is providedin the second bypass passage; and in that, during heating operation, thebypass flow rate regulation valve is opened.